Natural Cyclopeptide RA-XII, a New Autophagy Inhibitor, Suppresses Protective Autophagy for Enhancing Apoptosis through AMPK/mTOR/P70S6K Pathways in HepG2 Cells

Construction of a Multifunctional Upconversion Nanoplatform Based on Autophagy Inhibition and Photodynamic Therapy Combined with Chemotherapy for Antitumor Therapy

Inhibition of autophagy increases the sensitivity of tumor cells to radiotherapy and chemotherapy and improves the therapeutic effect on tumors. Recently, photodynamic therapy (PDT) combined with chemotherapy has been proven to further improve the efficiency of cancer treatment. As such, combining autophagy inhibition with PDT and chemotherapy may represent a potentially effective new strategy for cancer treatment. However, currently widely studied autophagy inhibitors inevitably produce various toxic side effects due to their inherent pharmacological activity. To overcome this constraint, in this study, we designed an ideal multifunctional upconversion nanoplatform, UCNP-Ce6-EPI@mPPA + NIR (MUCEN). Control, UCNP-EPI@mPPA (MUE), UCNP-EPI@mPPA + NIR (MUEN), Ce6-EPI@mPPA (MCE), Ce6-EPI@mPPA + NIR (MCEN), and UCNP-Ce6-EPI@mPPA (MUCE) groups were set up separately as controls. Based on a combination of autophagy inhibition and PDT, the average particle size of MUCEN was 197 nm, which can simultaneously achieve the double encapsulation of chlorine e6 (Ce6) and epirubicin (EPI). In vitro tests revealed that MUCE was efficiently endocytosed by 4T1 cells under near-infrared light irradiation. Further, in vivo tests revealed that MUCE dramatically inhibited tumor growth. Immunohistochemistry results indicated that MUCE efficiently increased the expression of autophagy inhibitors p62 and LC3 in tumor tissues. The synergistic effect of autophagy inhibition and PDT with MUCE exhibited superior tumor suppression, providing an innovative approach to cancer treatment.

Autophagy plays a pro-apoptotic role in arsenic trioxide-induced cell death of liver cancer

OBJECTIVE

The effects of arsenic trioxide (As2O3) on hepatocellular carcinoma have been documented widely. Autophagy plays dual roles in the survival and death of cancer cells. Therefore, we investigated the exact role of autophagy in As2O3-induced apoptosis in liver cancer cells.

METHODS

The viability of hepatoma cells was determined using the MTT assay with or without fetal bovine serum. The rate of apoptosis in liver cancer cells treated with As2O3 was evaluated using flow cytometry, Hoechst 33258 staining, and TUNEL assays. The rate of autophagy among liver cancer cells treated with As2O3 was detected using immunofluorescence, Western blot assay and transmission electron microscopy.

RESULTS

Upon treatment with As2O3, the viability of HepG2 and SMMC-7721 cells was decreased in a time- and dose-dependent manner. The apoptosis rates of both liver cancer cell lines increased with the concentration of As2O3, as shown by flow cytometry. Apoptosis in liver cancer cells treated with As2O3 was also shown by the activation of the caspase cascade and the regulation of Bcl-2/Bax expression. Furthermore, As2O3 treatment induced autophagy in liver cancer cells; this finding was supported by Western blot, immunofluorescence of LC3-II and beclin 1, and transmission electron microscopy. In liver cancer cells, As2O3 inhibited the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signal pathway that plays a vital role in both apoptosis and autophagy. The PI3K activator SC-79 partially reversed As2O3-induced autophagy and apoptosis. Furthermore, inhibiting autophagy with 3-methyladenine partially reversed the negative effects of As2O3 on cell viability. Serum starvation increased autophagy and amplified the effect of As2O3 on cell death.

CONCLUSION

As2O3 induces apoptosis and autophagy in liver cancer cells. Autophagy induced by As2O3 may have a proapoptotic effect that helps to reduce the viability of liver cancer cells. This study provides novel insights into the effects of As2O3 against liver cancer. Please cite this article as: Deng ZT, Liang SF, Huang GK, Wang YQ, Tu XY, Zhang YN, Li S, Liu T, Cheng BB. Autophagy plays a pro-apoptotic role in arsenic trioxide-induced cell death of liver cancer. J Integr Med. 2024; 22(3): 295-302.

The elastin-derived peptide (VGVAPG) activates autophagy in neuroblastoma (SH-SY5Y) cells via peroxisome proliferator-activated receptor gamma (PPARγ)

Autophagy is a self-degradative process important for balancing the sources of energy and involved in the development of Alzheimer's disease (AD). To date, a number of papers have shown that elastin-derived peptides (EDPs) affect the expression and activation of peroxisome proliferator-activated receptor gamma (PPARγ), which is crucial for the development of AD and autophagy initiation. Therefore, the aim of the present study was to determine whether EDPs with a Val-Gly-Val-Ala-Pro-Gly (VGVAPG) amino acid sequence activate the autophagic process in undifferentiated SH-SY5Y human neuroblastoma cells. Our study is the first to show that EDPs with the VGVAPG sequence initiate the autophagy process in the undifferentiated SH-SY5Y cell line exhibiting a number of features of normal neuroblasts. In particular, we observed in our study that VGAVPG peptide increased ULK1, AKT, PPARγ, and LC3B protein expression. Moreover, our experiments with the agonist (rosiglitazone) and antagonist (GW9662) of PPARγ confirm that the studied EDP acts through the PPARγ pathway affecting mTOR and finally autophagy. Some studies have shown that autophagy disturbances are involved in the development of AD. Therefore, we believe that our study will provide new evidence of the possible involvement of EDPs (especially VGVAPG) in the development of AD.

Autophagic mechanisms in longevity intervention: role of natural active compounds

The term 'autophagy' literally translates to 'self-eating' and alterations to autophagy have been identified as one of the several molecular changes that occur with aging in a variety of species. Autophagy and aging, have a complicated and multifaceted relationship that has recently come to light thanks to breakthroughs in our understanding of the various substrates of autophagy on tissue homoeostasis. Several studies have been conducted to reveal the relationship between autophagy and age-related diseases. The present review looks at a few new aspects of autophagy and speculates on how they might be connected to both aging and the onset and progression of disease. Additionally, we go over the most recent preclinical data supporting the use of autophagy modulators as age-related illnesses including cancer, cardiovascular and neurodegenerative diseases, and metabolic dysfunction. It is crucial to discover important targets in the autophagy pathway in order to create innovative therapies that effectively target autophagy. Natural products have pharmacological properties that can be therapeutically advantageous for the treatment of several diseases and they also serve as valuable sources of inspiration for the development of possible new small-molecule drugs. Indeed, recent scientific studies have shown that several natural products including alkaloids, terpenoids, steroids, and phenolics, have the ability to alter a number of important autophagic signalling pathways and exert therapeutic effects, thus, a wide range of potential targets in various stages of autophagy have been discovered. In this review, we summarised the naturally occurring active compounds that may control the autophagic signalling pathways.

Natural-Product-Mediated Autophagy in the Treatment of Various Liver Diseases

Autophagy is essential for the maintenance of hepatic homeostasis, and autophagic malfunction has been linked to the pathogenesis of substantial liver diseases. As a popular source of drug discovery, natural products have been used for centuries to effectively prevent the progression of various liver diseases. Emerging evidence has suggested that autophagy regulation is a critical mechanism underlying the therapeutic effects of these natural products. In this review, relevant studies are retrieved from scientific databases published between 2011 and 2022, and a novel scoring system was established to critically evaluate the completeness and scientific significance of the reviewed literature. We observed that numerous natural products were suggested to regulate autophagic flux. Depending on the therapeutic or pathogenic role autophagy plays in different liver diseases, autophagy-regulative natural products exhibit different therapeutic effects. According to our novel scoring system, in a considerable amount of the involved studies, convincing and reasonable evidence to elucidate the regulatory effects and underlying mechanisms of natural-product-mediated autophagy regulation was missing and needed further illustration. We highlight that autophagy-regulative natural products are valuable drug candidates with promising prospects for the treatment of liver diseases and deserve more attention in the future.

Anti-inflammatory activities of natural cyclopeptide RA-XII in colitis-associated colon cancer mouse model and its effect on gut microbiome

Colorectal cancer (CRC), the third most common cancer globally, is associated with intestinal inflammation that leads to poor prognosis. RA-XII, a natural cyclopeptide, has previously been reported to possess anti-tumor activities. Here, the anti-inflammatory activities of RA-XII were investigated in colitis-associated colon cancer mice and a co-culture in vitro model, in which colon cancer cells HCT116 and macrophages RAW264.7 were grown together to mimic the inflammatory microenvironment of CRC. Changes of inflammatory-related molecules and protein expressions in cells were evaluated after RA-XII incubation. Besides, azoxymethane and dextran sulfate sodium-induced colitis-associated colon cancer mice were treated with RA-XII for 24 days, inflammatory parameters and gut microbiome alterations were studied. Our results showed that RA-XII reversed the inflammatory responses of RAW264.7 cells induced by LPS and modulated the protein expressions of AKT, STAT3/p-STAT3, P70S6K, NF-κB and GSK3β and suppressed the expression of LC3A/B in HCT116 cells in co-culture system. RA-XII treatment restored the colitis damage in colon, reduced colon tumors numbers and decreased inflammatory factors (IL-6, IL-10 and TNF-α). The role of RA-XII on regulating gut microbiome was also demonstrated for the first time. In conclusion, our findings provided new scientific evidence for developing RA-XII as a potent anti-inflammatory agent for CRC.

Establishment of hairy root culture of Rubia yunnanensis Diels: Production of Rubiaceae-type cyclopeptides and quinones

Rubia yunnanensis is an important medicinal plant with various bioactive secondary metabolites. In order to reduce the dependence on wild populations of the species, we aim to establish in vitro culture system that can produce Rubiaceae-type cyclopeptides (RAs) and quinones. Agrobacterium rhizogenes-mediated transformation of stem segments of in vitro grown R. yunnanensis plants using four A. rhizogenes strains was studied and transformation conditions were optimized. Hairy roots appeared with the highest frequency (68.89%) when stem segments (with leaves) without pre-culture were immersed in A. rhizogenes A4 strain bacterial suspension for 30 min, co-cultured on Murashige and Skoog (MS) solid medium in the dark for three days, and afterwards incubated in darkness. PCR analysis of rolB and rolC genes confirmed transformed nature of six hairy root clones. The hairy roots grew rapidly, especially showing the highest accumulation of biomass in MS liquid medium compared to in vitro grown plants and calli. Histological observation of hairy root revealed anatomical difference in vascular cylinder, where the cells exhibited high mitotic activity characterized by vigorous growth. The UPLC-MS/MS analysis revealed that the amount of RAs in the hairy roots grown in ½MS liquid medium (4.611 μg g^-1 DW) was higher than that in in vitro grown plants (0.331 and 4.096 μg g^-1 DW for shoots and roots respectively) and calli (1.082 μg g^-1 DW), but still far lower than that in the roots of seed-borne plants (80.296 μg g^-1 DW). However, the hairy roots accumulated high level of quinones (2320.923 and 5067.801 μg g^-1 DW for MS and ½MS liquid media respectively), of the same order of magnitude as the roots of seed-borne plants (7409.973 μg g^-1 DW). Hairy root culture of R. yunnanensis, with high accumulation of biomass and production of quinones, may offer an attractive perspective for the production of the RAs and quinones that could be further optimized for pharmaceutical use.

Diversity of cultivable endophytic fungi in two Rubia plants and their potential for production of anti-tumour Rubiaceae-type cyclopeptides

Rubia plants are one of the most important plant resources possessing significant commercial and medicinal values. Plant endophytes could benefit their host plants in different ways. Rubiaceae-type cyclopeptides (RAs), mainly isolated from Rubia plants, have attracted considerable attentions for their distinctive bicyclic structures and significant antitumor activities, but their contents in plants are low. The aim of this study is to investigate the diversity of endophytic fungi in Rubia plants and their potential for production of RAs. In this work, 143 endophytic fungi isolates were obtained from two Rubia plants. Phylogenetic analysis was performed based on the ITS rDNA sequences, and the isolates were classified into 29 genera. Among them, four endophytic fungal strains were found to produce anti-tumour RAs by LC-MS/MS analysis. This work successfully provides valuable knowledges of endophytic fungi microbiome in Rubia plants for agricultural and industrial applications, and exploits a new environmental-friendly resource of RAs.

Advances in autophagy as a target in the treatment of tumours

Autophagy is a multi-step lysosomal degradation process, which regulates energy and material metabolism and has been used to maintain homeostasis. Autophagy has been shown to be involved in the regulation of health and disease. But at present, there is no consensus on the relationship between autophagy and tumour, and we consider that it plays a dual role in the occurrence and development of tumour. That is to say, under certain conditions, it can inhibit the occurrence of tumour, but it can also promote the process of tumour. Therefore, autophagy could be used as a target for tumour treatment. The regulation of autophagy plays a synergistic role in the radiotherapy, chemotherapy, phototherapy and immunotherapy of tumour, and nano drug delivery system provides a promising strategy for improving the efficacy of autophagy regulation. This review summarised the progress in the regulatory pathways and factors of autophagy as well as nanoformulations as carriers for the delivery of autophagy modulators.

Hyaluronic Acid Coated Liposomes Co-Delivery of Natural Cyclic Peptide RA-XII and Mitochondrial Targeted Photosensitizer for Highly Selective Precise Combined Treatment of Colon Cancer

Background

Natural cyclopeptide RA-XII, isolated from Rubia yunnanensis, is a promising chemotherapeutic agent for colon cancer. The photosensitizer protoporphyrin-IX attached with triphenylphosphonium (TPP) could possess mitochondria targeting capacity and exert photodynamic therapy (PDT) by inducing oxidizing damage to the mitochondria and cell apoptosis eventually. In this work, pH-sensitive liposomes were constructed to simultaneously deliver RA-XII as a chemotherapeutic drug and modified porphyrin as a mitochondria-targeting photosensitizer to treat colon cancer, and verified its mechanism of action and antitumor therapeutic efficacy.

Methods

The colon cancer targeting liposome nanoparticle RA/TPPP-Lip was synthesized using thin film hydration. The therapeutic effect and targeting ability of RA/TPPP-Lip was investigated in vitro. And use HCT116 cell allogeneic subcutaneous transplantation tumor model to investigate the anti-tumor and targeting effects of RA/TPPP-Lip in vivo.

Results

RA/TPPP-Lip gained the targeting ability through surface-modified HA to increase the accumulation of RA-XII and TPPP in colon cancer cells. A series of in vitro experimental results showed that TPPP produced cytotoxic ROS under laser irradiation to directly damage cell mitochondria and played a combined role with RA-XII, making RA/TPPP-Lip the best colon cancer cell growth inhibitory effect. Furthermore, in vivo antitumor experiments showed that the RA/TPPP-Lip substantially accumulated at the tumor site and efficiently repressed tumor growth in nude mice.

Conclusion

We have successfully designed a new cancer-targeted nanomedicine platform (RA/TPPP-Lip) for the collaborative treatment of colon cancer, which can achieve the targeted continuous release of multiple therapeutic drugs. This work provides a new strategy for precise combination therapy, which may promote the further development of collaborative cancer treatment platforms.

Natural Cyclopeptides as Anticancer Agents in the Last 20 Years

Cyclopeptides or cyclic peptides are polypeptides formed by ring closing of terminal amino acids. A large number of natural cyclopeptides have been reported to be highly effective against different cancer cells, some of which are renowned for their clinical uses. Compared to linear peptides, cyclopeptides have absolute advantages of structural rigidity, biochemical stability, binding affinity as well as membrane permeability, which contribute greatly to their anticancer potency. Therefore, the discovery and development of natural cyclopeptides as anticancer agents remains attractive to academic researchers and pharmaceutical companies. Herein, we provide an overview of anticancer cyclopeptides that were discovered in the past 20 years. The present review mainly focuses on the anticancer efficacies, mechanisms of action and chemical structures of cyclopeptides with natural origins. Additionally, studies of the structure-activity relationship, total synthetic strategies as well as bioactivities of natural cyclopeptides are also included in this article. In conclusion, due to their characteristic structural features, natural cyclopeptides have great potential to be developed as anticancer agents. Indeed, they can also serve as excellent scaffolds for the synthesis of novel derivatives for combating cancerous pathologies.

TNFα enhances trovafloxacin-induced in vitro hepatotoxicity by inhibiting protective autophagy

Trovafloxacin (TVX) is associated with idiosyncratic drug-induced liver injury (iDILI) and inflammation-mediated hepatotoxicity. However, the inflammatory stress-regulated mechanisms in iDILI remain unclear. Herein, we elucidated the novel role of tumor-necrosis factor alpha (TNFα), an inflammatory stress factor, in TVX-induced in vitro hepatotoxicity and synergistic toxicity. TVX specifically induced synergistic toxicity in HepG2 cells with TNFα, which inhibits autophagy. TVX-treated HepG2 cells induced protective autophagy by inhibiting the expression of mTOR signaling proteins, while ATG5 knockdown in HepG2 cells, responsible for the impairment of autophagy, enhanced TVX-induced toxicity due to the increase in cytochrome C release and JNK pathway activation. Interestingly, the expression of mTOR signal proteins, which were suppressed by TVX, disrupted the negative feedback of the PI3K/AKT pathway and TNFα rebounded p70S6K phosphorylation. Co-treatment with TVX and TNFα inhibited protective autophagy by maintaining p70S6K activity, which enhanced TVX-induced cytotoxicity. Phosphorylation of p70S6K was inhibited by siRNA knockdown and rapamycin to restore TNFα-inhibited autophagy, which prevented the synergistic effect on TVX-induced cytotoxicity. These results indicate that TVX activates protective autophagy in HepG2 cells exposed to toxicity and an imbalance in negative feedback regulation of autophagy by TNFα synergistically enhanced the toxicity. The finding from this study may contribute to a better understanding of the mechanisms underlying iDILI associated with inflammatory stress.

RA-XII, a bicyclic hexapeptidic glucoside isolated from Rubia yunnanensis Diels, exerts antitumor activity by inhibiting protective autophagy and activating Akt-mTOR pathway in colorectal cancer cells

ETHNOPHARMACOLOGICAL RELEVANCE

The roots of Rubia yunnanensis Diels (Chinese name 'Xiao-Hong-Shen'), a traditional Chinese medicine native to Yunnan province (China), have a long history of use for treating several diseases, such as tuberculosis, rheumatism and cancers. A bicyclic hexapeptidic glucoside named RA-XII was isolated from R. yunnanensis, which has been reported to exert anti-inflammatory and antitumor activities.

AIM OF THE STUDY

This study was designed to investigate the antitumor activity and potential mechanism of RA-XII on colorectal cancer (CRC) cell lines.

MATERIALS AND METHODS

Sulforhodamine B assay, clonogenic assay and cell cycle analysis were conducted to assess the anti-proliferative activity of RA-XII on CRC cells. GFP-LC3B plasmid transfection, MDC and AO staining assays, cathepsin activity assay, and siRNAs against several genes were used to investigate the effect of RA-XII on autophagy. Western blotting was used to examine the expression levels of proteins associated with cell cycle arrest, apoptosis and autophagy. Human CRC xenograft-bearing BALB/c nude mice were used to evaluate the antitumor effect of RA-XII in vivo.

RESULTS

RA-XII showed favorable antineoplastic activity in SW620 and HT29 cells in vitro and in vivo. RA-XII did not induce apoptosis indicated by no obvious changes on mitochondrial membrane potential and apoptosis-related marker proteins in SW620 or HT29 cells. Treatment of RA-XII inhibited the formation of autophagosomes, which is implied by the GFP-LC3 fluorescent dots, MDC-stained autophagic vesicles and LC3 protein expression. It was indicated that RA-XII suppressed autophagy by regulating several signaling pathways including mTOR and NF-κB pathways. Pharmacological or genetic inhibition of autophagy could enhance the cytotoxicity of RA-XII while autophagy inducer could rescue RA-XII-induced cell death. Besides, RA-XII could increase the susceptibility of CRC cells to bortezomib.

CONCLUSION

Our study demonstrated that RA-XII exerted antitumor activity independent of apoptosis, and suppressed protective autophagy by regulating mTOR and NF-κB pathways in SW620 and HT29 cell lines, which suggested that RA-XII is a key active ingredient for the cancer treatment of Rubia yunnanensis and possesses a promising prospect as an autophagy inhibitor for CRC therapy.

Targeting signal pathways triggered by cyclic peptides in cancer: Current trends and future challenges

Cancer is a global health issue that origins thousands of deaths annually worldwide. Cyclic peptides are polypeptide chains which are formed by cyclic sequence of amide bonds between proteinogenic or non-proteinogenic amino acids. Numerous evidences indicate that cyclic peptides are implicated with the occurrence and development of cancer. This review presents the current knowledge about the role of cyclic peptides in cancer, such as liver cancer, colorectal cancer, ovarian cancer, breast cancer as well as prostate cancer. Specifically, the precise molecular mechanisms between cyclic peptides and cancer are elaborated. Some cyclic peptides from nature and synthesis prevent the occurrence and development of cancer. However, some other cyclic peptides including endothelin-1, urotensinⅡand melanin-concentrating hormone deteriorate the pathogenesis of cancer. Given the pleiotropic actions of cyclic peptides, the identification and development of cyclic peptides and their derivates as drug may be a potent therapeutic strategy for cancer.

Periplocin inhibits the growth of pancreatic cancer by inducing apoptosis via AMPK-mTOR signaling

BACKGROUND

Periplocin is a monomeric compound that exhibits anti-tumor activities. It is extracted from Cortex Periplocae.

OBJECTIVE

This study aimed at determining the effect of periplocin treatment on the apoptosis and proliferation of human pancreatic cancer cells, and to elucidate on its mechanisms of action.

METHODS

PANC1 and cfpac1 cells were treated with periplocin. Cell proliferation was detected by RTCA, Ki67 immunofluorescence, and a clonogenic assay. The transwell assay was used to examine cell migration and invasion functions. The expression of apoptosis-associated proteins was detected by flow cytometry and western blotting. Total RNA was extracted from the treated and untreated group of PANC1 cells for RNA-seq detection and analysis. Differentially expressed genes were screened for GO biological process and KEGG pathway analysis. Finally, CFPAC1 cells were subcutaneously inoculated into BALB / c nude mice to assess tumor growth.

RESULTS

Periplocin inhibited the proliferation of PANC1 and CFPAC1 cells and induced their apoptosis by activating the AMPK/mTOR pathway and inhibiting p70 S6K. It also attenuated the cell migration, invasion, and inhibited the growth of cfpac1 xenografts in nude mice.

CONCLUSIONS

Periplocin inhibits human pancreatic cancer cell proliferation and induces their apoptosis by activating the AMPK / mTOR pathway.

The Role of Autophagy in Liver Cancer: Crosstalk in Signaling Pathways and Potential Therapeutic Targets

Autophagy is an evolutionarily conserved lysosomal-dependent pathway for degrading cytoplasmic proteins, macromolecules, and organelles. Autophagy-related genes (Atgs) are the core molecular machinery in the control of autophagy, and several major functional groups of Atgs coordinate the entire autophagic process. Autophagy plays a dual role in liver cancer development via several critical signaling pathways, including the PI3K-AKT-mTOR, AMPK-mTOR, EGF, MAPK, Wnt/β-catenin, p53, and NF-κB pathways. Here, we review the signaling pathways involved in the cross-talk between autophagy and hepatocellular carcinoma (HCC) and analyze the status of the development of novel HCC therapy by targeting the core molecular machinery of autophagy as well as the key signaling pathways. The induction or the inhibition of autophagy by the modulation of signaling pathways can confer therapeutic benefits to patients. Understanding the molecular mechanisms underlying the cross-link of autophagy and HCC may extend to translational studies that may ultimately lead to novel therapy and regimen formation in HCC treatment.

Costunolide and dehydrocostuslactone from Saussurea lappa root inhibit autophagy in hepatocellular carcinoma cells

Autophagy is a catabolic process for degradation of intracellular components and plays an important role in the development and growth of cancer. Our preliminary screening confirmed that an extract from the root of Saussurea lappa remarkably suppressed the proliferation of HepG2 hepatocellular carcinoma cells and inhibited autophagy. In this study, we explored the effects of costunolide (CL) and dehydrocostuslactone (DCL), which are bioactive sesquiterpene lactones in this extract, on autophagy modulation in HepG2 cells. An analysis of autophagy-related proteins demonstrated that CL and DCL blocks the autophagy process that leads to the accumulation of microtubule-associated protein 1 light chain 3 (LC3) and SQSTM1/p62 (p62). LC3 turnover assays indicated that CL and DCL trigger autophagy inhibition by blocking the autophagic flux, thereby resulting in the accumulation of LC3-II and p62. These results are encouraging and warrant further study of CL and DCL for potential use as autophagy inhibiting agents for liver cancer therapy.

Kidney targeted delivery of asiatic acid using a FITC labeled renal tubular-targeting peptide modified PLGA-PEG system

Chronic kidney disease (CKD) is one of the leading public health problems worldwide and finally progresses to end-stage renal disease. The therapeutic options of CKD are very limited. Thus, development of drug delivery systems specific-targeting to kidney may offer more options. Here we developed an efficient kidney-targeted drug delivery system using a FITC labeled renal tubular-targeting peptide modified PLGA-PEG nanoparticles and investigated the intrarenal distribution and cell-type binding. We found that the modified nanoparticles with an approximate diameter of 200 nm exhibited the highest binding capacity with HK-2 cells and fluorescence and immunohistochemical analysis showed they mainly localized in renal proximal tubules by passing through the basolateral side. Furthermore, these kidney-specific nanoparticles could significantly enhance the therapeutic effects of asiatic acid, an insoluble triterpenoid compound as drug delivery carriers. In conclusion, these results suggest the potential of the peptide modified PLGA-PEG nanoparticles as kidneytargeted drug delivery system to proximal tubular cells in treatment of CKD.

Autophagy-modulating phytochemicals in cancer therapeutics: Current evidences and future perspectives

Autophagy is an intracellular catabolic self-cannibalism that eliminates dysfunctional cytoplasmic cargos by the fusion of cargo-containing autophagosomes with lysosomes to maintain cyto-homeostasis. Autophagy sustains a dynamic interlink between cytoprotective and cytostatic function during malignant transformation in a context-dependent manner. The antioxidant and immunomodulatory phyto-products govern autophagy and autophagy-associated signaling pathways to combat cellular incompetence during malignant transformation. Moreover, in a close cellular signaling circuit, autophagy regulates aberrant epigenetic modulation and inflammation, which limits tumor metastasis. Thus, manipulating autophagy for induction of cell death and associated regulatory phenomena will embark on a new strategy for tumor suppression with wide therapeutic implications. Despite the prodigious availability of lead pharmacophores in nature, the central autophagy regulating entities, their explicit target, as well as pre-clinical and clinical assessment remains a major question to be answered. In addition to this, the stage-specific regulation of autophagy and mode of action with natural products in regulating the key autophagic molecules, control of tumor-specific pathways in relation to modulation of autophagic network specify therapeutic target in caner. Moreover, the molecular pathway specificity and enhanced efficacy of the pre-existing chemotherapeutic agents in co-treatment with these phytochemicals hold high prevalence for target specific cancer therapeutics. Hence, the multi-specific role of phytochemicals in a cellular and tumor context dependent manner raises immense curiosity for investigating of novel therapeutic avenues. In this perspective, this review discusses about diverse implicit mechanisms deployed by the bioactive compounds in diagnosis and therapeutics approach during cancer progression with special insight into autophagic regulation.

Alpha7 Nicotinic Acetylcholine Receptor Alleviates Inflammatory Bowel Disease Through Induction of AMPK-mTOR-p70S6K-Mediated Autophagy

Alpha7 nicotinic acetylcholine receptor (α7nAChR) has been reported to be protective in several kinds of disorders through inflammatory suppression. Here, we investigated the role of α7nAChR in inflammatory bowel disease (IBD) on α7nAChR deficient mice (α7nAChR^-/-) and the wild-type mice (α7nAChR^+/+). Three percent dextran sulfate sodium (DSS) was used for the creation of IBD mice model and lipopolysaccharides (LPS)/DSS as an inflammatory stressor in murine bone marrow-derived macrophages (BMDMs). The severity of IBD was determined and HE staining as well as enzyme-linked immunosorbent assay (ELISA) and real-time PCR were used to detect the level of inflammatory activation. Western blot was used to determine the levels of autophagy-related proteins. Transmission electron microscopy and mRFP-GFP-LC3 plasmid were applied to determine the levels of autophagy. We demonstrated that deficiency in α7nAChR produced a detrimental effect on IBD severity and inflammatory reaction in DSS-induced colitis models. Those effects were led to via autophagy dysfunction. α7nAChR deficiency attenuated the protective and anti-inflammatory effect of autophagy inducer in IBD mice and BMDMs challenged with LPS/DSS. The alleviative effect of activating α7nAChR was attenuated through inhibiting adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-mediated signaling. In conclusion, α7nAChR contributes to alleviate IBD through the induction of AMPK-mammalian target of rapamycin rabbit (mTOR)-p70 ribosomal protein S6 kinase (p70S6K)-mediated autophagy, thus providing a novel target for the treatment of IBD.

Selection and Validation of Appropriate Reference Genes for Quantitative RT-PCR Analysis in Rubia yunnanensis Diels Based on Transcriptome Data

Real-time quantitative polymerase chain reaction (RT-qPCR) has been widely applied in gene expression and transcription abundance analysis because of its high sensitivity, good repeatability, and strong specificity. Selection of relatively stable reference genes is a precondition in order to obtain the reliable analysis results. However, little is known about evaluation of a set of reference genes through scientific experiments in Rubia plants. Here, 15 candidate reference genes were selected from R. yunnanensis transcriptome database and analyzed under abiotic stresses, hormone treatments, and different tissues. Among these 15 candidate reference genes, heterogeneous nuclear ribonucleoprotein (hnRNP), TATA binding protein (TBP), ribosomal protein L5 (RPL5), malate dehydrogenase (MDH), and elongation factor 1-alpha (EF-1α) were indicated as the five most stable reference genes by four statistical programs (geNorm, NormFinder, BestKeeper, and RefFinder). Ultimately, the validity of reference genes was confirmed by normalizing the expression of o-succinylbenzoate-CoA ligase (OSBL) and isochorismate synthase (ICS) involved in the anthraquinone biosynthesis pathway in different tissues and hormone treatments. Meanwhile, four other putative genes involved in the anthraquinone biosynthesis pathway were also normalized with the selected reference genes, which showed similar expression levels with those given by transcriptome data. This work is the first research that aims at a systematic validation on the stability of reference genes selected from R. yunnanensis transcriptome data and will be conducive to analyze gene expression in R. yunnanensis or other Rubia species.

Rhein induces liver cancer cells apoptosis via activating ROS-dependent JNK/Jun/caspase-3 signaling pathway

Background: Liver cancer is one of the leading cancers in China. Rhein induces apoptosis in various human cancer cells, but the underlying mechanism is still unknown.

Methods: In the present study, the MTT assay was used to detect the anti-cell growth ability of Rhein on liver cancer cells. Hoechst33342 staining and FACS assay were used to detect cell apoptosis. Finally, the effect of Rhein on JNK protein' phosphorylation level and the apoptosis-associated proteins were determined by western blot.

Results: Here, we found that Rhein significantly inhibited the cell viability in a dose-dependent and time-dependent manner both in HepG2 and Huh7 cells. Also, Rhein increased the apoptosis, mitochondrial membrane potential (MMP) and cell-cycle arrest. Furthermore, we observed that the ROS level and JNK/Jun/caspase-3 signaling pathway played a key role in Rhein induced apoptosis. Our study further demonstrated that Rhein increases apoptosis by inducing the generation of ROS and activating the JNK/Jun/caspase-3 signaling pathway.

Conclusions: The present study showed that Rhein promotes apoptosis via regulating ROS/JNK/Jun/caspase-3 signaling pathway both in HepG2 and Huh7 cells. Rhein may be a promising therapeutic candidate for the treatment of liver cancer.

The Upstream Pathway of mTOR-Mediated Autophagy in Liver Diseases

Autophagy, originally found in liver experiments, is a cellular process that degrades damaged organelle or protein aggregation. This process frees cells from various stress states is a cell survival mechanism under stress stimulation. It is now known that dysregulation of autophagy can cause many liver diseases. Therefore, how to properly regulate autophagy is the key to the treatment of liver injury. mechanistic target of rapamycin (mTOR)is the core hub regulating autophagy, which is subject to different upstream signaling pathways to regulate autophagy. This review summarizes three upstream pathways of mTOR: the phosphoinositide 3-kinase (PI3K)/protein kinase (AKT) signaling pathway, the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway, and the rat sarcoma (Ras)/rapidly accelerated fibrosarcoma (Raf)/mitogen-extracellular activated protein kinase kinase (MEK)/ extracellular-signal-regulated kinase (ERK) signaling pathway, specifically explored their role in liver fibrosis, hepatitis B, non-alcoholic fatty liver, liver cancer, hepatic ischemia reperfusion and other liver diseases through the regulation of mTOR-mediated autophagy. Moreover, we also analyzed the crosstalk between these three pathways, aiming to find new targets for the treatment of human liver disease based on autophagy.

RCE‑4, a potential anti‑cervical cancer drug isolated from Reineckia carnea, induces autophagy via the dual blockade of PI3K and ERK pathways in cervical cancer CaSki cells

The steroidal saponin RCE‑4 (1β, 3β, 5β, 25S)‑spirostan‑1, 3‑diol 1‑[α‑L‑rhamnopyranosyl‑(1→2)‑β‑D‑xylopyranoside], isolated from Reineckia carnea, exerts significant anti‑cervical cancer activity by inducing apoptosis. The potential effect of RCE‑4 on proliferation inhibition and autophagy induction has rarely been studied. Therefore, the focus of the present study was to investigate the effects of RCE‑4 on proliferation, and to elucidate the detailed mechanisms involved in autophagy induction in cervical cancer cells. CaSki cells were treated with RCE‑4 or/and autophagy inhibitors, and the effect of RCE‑4 on cellular proliferation was assessed by MTT assay. The pro‑autophagic properties of RCE‑4 were subsequently confirmed using monomeric red fluorescent protein‑green fluorescent protein‑microtubule‑associated proteins 1A/1B light chain 3B (LC3) adenoviruses and CYTO‑ID autophagy assays, and by assessing the accumulation of lipid‑modified LC3 (LC3II). The mechanisms of RCE‑4‑induced autophagy were investigated by western blot analysis. The results demonstrated that inhibiting autophagy significantly promoted RCE‑4‑induced cell death, indicating that autophagy served a protective role following RCE‑4 treatment. In addition, RCE‑4‑induced autophagy was reflected by increased expression levels of the serine/threonine‑protein kinase ULK1, phosphorylated (p)‑ULK1, p‑Beclin‑1 and LC3II, the formation of autophagosomes and autolysosomes, and sequestosome 1 (p62) degradation. Subsequent analysis indicated that RCE‑4 activated the AMP‑activated protein kinase (AMPK) pathway by upregulating AMPK and p‑AMPK, and also inhibited the PI3K and extracellular signal‑regulated kinase (ERK) signaling pathways by downregulating p‑PI3K, p‑Akt, p‑mTOR, Ras, c‑Raf, p‑c‑Raf, dual specificity mitogen‑activated protein kinase kinase (MEK)1/2, p‑MEK1/2 and p‑Erk1/2. Additionally, with increased treatment times RCE‑4 may impair lysosomal cathepsin activity and inhibit autophagy flux by suppressing the expression of AMPK, p‑AMPK, ULK1, p‑ULK1 and p‑Beclin‑1, and upregulating that of p62. These results indicated that the dual RCE‑4‑induced inhibition of the PI3K and ERK pathways may result in a more significant anti‑tumor effect and prevent chemoresistance, compared with the inhibition of either single pathway; furthermore, dual blockade of PI3K and ERK, and the AMPK pathway may be involved in the regulation of autophagy caused by RCE‑4. Taken together, RCE‑4 induced autophagy to protect cancer cells against apoptosis, but AMPK‑mediated autophagy was inhibited in the later stages of RCE‑4 treatment. In addition, autophagy inhibition improved the therapeutic effect of RCE‑4. These data highlight RCE‑4 as a potential candidate for cervical cancer treatment.

MLK3 silence induces cervical cancer cell apoptosis via the Notch-1/autophagy network

Mixed-lineage kinase 3 (MLK3), the mitogen-activated protein kinase kinase kinase (MAP3K), has been recognized as a player in tumorigenesis and oncogenic signalling, yet its detailed functions and signalling in cervical cancer have not been fully elucidated. Here, we identify that cervical cancer cells display higher mRNA and protein levels of MLK3 than normal cervical epithelial squamous cells. In HeLa and SiHa cell, MLK3 knockdown using siRNA remarkably suppressed cell survival and promoted cell apoptosis, with increased expression of the apoptosis-related protein Bax and reduced Bcl-2. Moreover, MLK3 knockdown promoted cell autophagy, demonstrated by increased ratio of autophagy-related proteins LC3II/LC3I and decreased p62 expression in MLK3 depletion cells. Furthermore, MLK3 knockdown remarkably abolished Notch-1 expression in cervical cancer cells. By co-treating Hela cells with MLK3 specific siRNA and pcDNA3.1-Notch-1 overexpression plasmid or autophagy inhibitor 3-MA, we found that MLK3 played its role in cervical cancer cells via the Notch-1/autophagy network. Our results demonstrate the importance of MLK3 in cervical cancer progression via modulating the Notch-1/autophagy network, and suggest that MLK3 is a promising therapeutic target for cervical cancer.

Combining use of Phillyrin and autophagy blocker alleviates laryngeal squamous cell carcinoma via AMPK/mTOR/p70S6K signaling

Phillyrin (PHN), one of the major active constituents of Forsythia suspensa and F. koreana, has been reported to produce antioxidant, antibacterial, anti-obesity and anti-inflammatory effects. However, no study has demonstrated the role of PHN in laryngeal squamous cell carcinoma (LSCC). We aimed to investigate the effects of PHN on the proliferation and apoptosis of HEp-2 cells. In the present study, PHN alone showed little effect on HEp-2 cell proliferation and apoptosis. Subsequent tests showed that PHN could largely enhance the level of autophagy on HEp-2 cells. Combining use of PHN and autophagy blockers including 3-methyladenine (3-MA) and chloroquine (CQ) significantly inhibited HEp-2 cell proliferation in a dose- and time-dependent manner and induced apoptosis after 24 h in a dose-dependent manner. Additionally, we found that the possible underlying molecular mechanism of PHN-induced autophagy might be through the AMPK/mTOR/p70S6K signaling pathway. Taken together, our study indicates that combining use of PHN and autophagy blockers may serve as a novel strategy in LSCC treatment.

Screening of Crude Drugs Used in Japanese Kampo Formulas for Autophagy-Mediated Cell Survival of the Human Hepatocellular Carcinoma Cell Line

Background: Autophagy is a catabolic process through which dysfunctional proteins and organelles are degraded, and that is associated with the proliferation of cancer cells. The aim of this study was to screen approximately 130 kinds of crude drugs used in Japanese Kampo formulas to identify crude drugs that would regulate the proliferation through autophagy of human hepatocellular carcinoma HepG2 cells. Methods: Extracts of each crude drug were prepared using methanol. Protein levels were determined using Western blotting. Cell viability was measured by MTT assay. Results: Among the 130 crude extracts, 24 of them increased LC3-II expression. Among these, Goboshi (burdock fruit), Soboku (sappan wood), Mokko (saussurea root), Rengyo (forsythia fruit), and Hikai (dioscorea) notably suppressed the proliferation of HepG2 cells and increased p62 expression levels, which suggested that these five extracts downregulate the autophagic activity resulting in the accumulation of p62. On the other hand, Hishinomi (water chestnut), Biwayo (loquat leaf), and Binroji (areca) induced cell growth and decreased or were uninvolved with p62 expression levels, which implied that these three extracts might induce autophagy modulators for cell growth. Conclusions: The results suggest that the compounds contained in the crude drugs selected for this study could control cell viability by regulating autophagic activity in HepG2 cells. The isolation and identification of the active compounds in these drugs might lead to the development of agents for autophagy research and cancer chemoprevention.

RA-XII Suppresses the Development and Growth of Liver Cancer by Inhibition of Lipogenesis via SCAP-dependent SREBP Supression

Lipogenesis plays a critical role in the growth and metastasis of tumors, which is becoming an attractive target for anti-tumor drugs. RA-XII, one of the cyclopeptide glycosides isolated from Rubia yunnanensis, exerts anti-tumor effects on liver cancer. However, the underlying mechanisms are not clear. In the present study, the effects of RA-XII on lipogenesis were evaluated and the underlying mechanisms were investigated. The results indicated that RA-XII strongly inhibited tumor growth and lipogenesis (triglycerides and lipid droplets) in HepG2 cells, and the expression of key factors involved in lipogenesis (SREBP, SCD, FASN) was also obviously downregulated. Further investigation showed that the anti-tumor effects of RA-XII were attenuated by SREBP knockdown. Moreover, RA-XII downregulated the expression of SREBP cleavage-activating protein (SCAP), an upstream regulator of SREBP, and siRNA of SCAP prevented its restrained effects on tumor growth and lipogenesis. In addition, the in vivo experiment showed that RA-XII strongly restrained the lipogenesis and growth of liver tumor in nude mice xenograft model. Taken together, these results indicate that RA-XII suppresses the liver cancer growth by inhibition of lipogenesis via SCAP-dependent SREBP suppression. The findings reveal the potentials of RA-XII to be used in a novel therapeutic approach for treating liver cancer.

Inhibition of fatty acid synthesis arrests colorectal neoplasm growth and metastasis: Anti-cancer therapeutical effects of natural cyclopeptide RA-XII

Emerging evidence has shown that metabolism, in particular the synthesis of fatty acids, has great significance for growth and metastasis of colorectal neoplasm. The previous results showed that RA-XII, a natural cyclopeptide isolated from Rubia yunnanensis, inhibits tumor growth and metastasis by AMPK/mTOR/P70S6K pathway and PI3K/AKT/NF-κB pathway. But if or not lipid metabolism involves the antitumor mechanism of RA-XII is not clear. Herein the results indicated that RA-XII reduced the cell motility by decreasing the expressions of β-catenin and β-catenin dependent proteins CD44 and MMP7 in HCT116 cells. Then RA-XII effectively reduced fatty acids levels by decreasing the expression of SREBP-1 and inhibiting the expressions of de novo fatty acid synthesis proteins FASN and SCD. Moreover the decreased cell motility caused by RA-XII was attenuated with the SREBP-1 knockdown. In addition, the in vivo experiments also demonstrated that RA-XII inhibited tumor growth and metastasis via restraining lipogenesis in colorectal neoplasm mouse models. Taken together, these results indicated that RA-XII suppressed the colorectal neoplasm growth and metastasis by inhibition of lipogenesis depended on SREBP-1 suppression.

Rubipodanin B, a New Cytotoxic Cyclopeptide from Rubia podantha

Using the TLC cyclopeptide protosite detection method, a new cyclohexapeptide named rubipodanin B (1), together with 11 known Rubiaceae-type cyclopeptides (RAs), RA-X-OMe (2), RA-IV (3), RA-XI (4), RA-XIII-OMe (5), rubiyunnanin C (6), RA-I (7), RA-III (8), RA-V (9), RA-VII (10), RA-XII (11) and rubipodanin A (12), were obtained from the roots and rhizomes of Rubia podantha Diels. The structures were determined using various spectroscopic methods. Among them, 2 was firstly identified as a natural product, and 3-6 were firstly isolated from this species. Cytotoxicity and NF-κB signaling pathway activity of 1, 2, 4, 6, 7 and 9 were evaluated. All these compounds showed cytotoxic activities against three human tumor cell lines, MDA-MB-231, SW620 and HepG2, with the IC₅₀ values between 0.015 and 10.27 μm, and only 7 and 9 possessed NF-κB inhibitory activities with the IC₅₀ values of 2.42 and 0.046 μm, respectively, which demonstrated that 2-alanine amino acid plays a key role to maintain the RAs bioactivity.

Resveratrol, an activator of SIRT1, induces protective autophagy in non-small-cell lung cancer via inhibiting Akt/mTOR and activating p38-MAPK

Background

Resveratrol, a natural polyphenolic phytoalexin, has potent anti-tumor activity. Recently, it was found to induce autophagy in cancer cells. However, the effects of resveratrol on autophagy in non-small-cell lung cancer (NSCLC) cells have not yet been clearly elucidated.

Materials and methods

A549 and H1299 cells were treated with different concentrations of resveratrol. Cell growth and apoptosis were measured by CCK-8 assay and flow cytometry, respectively. A549 cells were then treated with 200 μM resveratrol or SRT1720. Cell autophagy was detected by western blot and immunofluorescence.

Results

In this study, we found that resveratrol exerted the anti-tumor effect through inhibiting cell proliferation and promoting cell apoptosis in NSCLC cells dose-dependently. Resveratrol has also increased the relative expression of Beclin1 and LC3 II/I while decreased p62 expression, suggesting that resveratrol induced autophagy in NSCLC cells. In addition, resveratrol increased SIRT1 expression and SIRT1 activator SRT1720-induced autophagy of NSCLC cells. SIRT1 knockdown reduced resveratrol-induced autophagy significantly. These results indicated that resveratrol might induce autophagy through upregulating SIRT1 expression. Moreover, inhibiting autophagy by autophagy inhibitor 3-methyladenine or SIRT1 inhibitor nicotinamide significantly suppressed proliferation while promoted apoptosis compared with the resveratrol 200 μM group, suggesting that resveratrol-induced autophagy might act as a protective mechanism to promote NSCLC cell survival and inhibiting autophagy can enhance the anti-tumor effect of resveratrol. Besides that, resveratrol treatment inhibited Akt/mTOR while p38-MAPK was activated in NSCLC cells in a dose-dependent manner. Activating Akt/ mTOR pathway by IGF-1 or inhibiting p-38-MAPK pathway by doramapimod significantly inhibited cell proliferation while increased cell apoptosis of NSCLC cells compared with the resveratrol 200 μM group.

Conclusion

Taken together, our findings suggest that resveratrol inhibited proliferation but induced apoptosis and autophagy via inhibiting Akt/mTOR and activating p38-MAPK pathway. Resveratrol-induced autophagy might act as a protective mechanism to promote NSCLC cell survival. Therefore, inhibition of autophagy may enhance the anti-tumor activity of resveratrol in NSCLC.

Sicilian Litchi Fruit Extracts Induce Autophagy versus Apoptosis Switch in Human Colon Cancer Cells

Litchi chinensis Sonnerat is a tropical tree whose fruits contain significant amounts of bioactive polyphenols. Litchi cultivation has recently spread in Sicily where the climate conditions are particularly favorable for this crop. Recent findings have shown that Litchi extracts display anti-tumor and pro-apoptotic effects in vitro, but the precise underlying mechanisms have not been fully elucidated. In this study, we report for the first time the effects of Sicilian litchi fruit extracts on colon cancer cells. The results indicated that litchi exocarp, mesocarp and endocarp fractions reduce the viability and clonogenic growth of HT29 cells. These effects were due to cell cycle arrest in the G2/M phase followed by caspase-dependent cell death. Interestingly, litchi exocarp and endocarp triggered a precocious autophagic response (16–24 h), which was accompanied by an increase in the level of autophagy related 1/autophagy activating kinase 1 (ATG1/ULK1), beclin-1, microtubule associated protein 1 light chain 3 (LC3)-II and p62 proteins. Autophagy inhibition by bafilomycin A1 or beclin-1 silencing increased cell death, thus suggesting that autophagy was initially triggered as a pro-survival response. Significant effects of Litchi extracts were also observed in other colon cancer cells, including HCT116 and Caco-2 cells. On the other hand, differentiated Caco-2 cells, a model of human enterocytes, appeared to be insensitive to the extracts at the same treatment conditions. High-Performance Liquid Chromatography–Electrospray Ionization-Quadrupole-Time-Of-Flight HPLC/ESI/Q-TOF evidenced the presence of some polyphenolic compounds, specifically in exocarp and endocarp extracts, that can account for the observed biological effects. The results obtained suggest a potential therapeutic efficacy of polyphenolic compounds purified from Sicilian Litchi fractions for the treatment of colon cancer. Moreover, our findings indicate that modulation of autophagy can represent a tool to improve the effectiveness of these agents and potentiate the anti-tumor response of colon cancer cells.